The invention relates to optical devices. More particularly, the invention relates to an interleaver/deinterleaver having a folded design such that an optical signal passes through a single crystal multiple times.
As telecommunications usage increases as a result of, for example increased Internet usage, increased types of communications, and population growth, telecommunications providers are required to provide greater voice- and data-carrying capacity. In order to reduce cost and the amount of time required to provide the increased capacity wavelength division multiplexing (WDM) and dense wavelength division multiplexing (DWDM) have been developed, which provide increased capacity without requiring new fiber optic cables.
WDM and DWDM technologies combine multiple optical signals into a single fiber by transporting different signals on different optical wavelengths or channels. Interleaving and deinterleaving of optical channels is typically accomplished with thin film optical filters. However, multiple layers of film are required to interleave and deinterleave multiple channels, which increases the cost and complexity of a component. Another disadvantage of multiple layers of thin film for filtering is that the thin films break down over time, especially when operating under high power conditions.
What is needed is an improved optical device for use with WDM and/or DWDM optical signals. Prior attempts to improve optical devices are disclosed in U.S. Pat. No. 4,566,761 issued Jan. 28, 1986 to Carlsen et al, U.S. Pat. No. 4,685,773 issued Aug. 11, 1987 to Carlsen et al, and U.S. Pat. No. 5,694,233 issued Dec. 2, 1997 to Wu et al, which are incorporated herein by reference.
The present invention relates to an interleaver/deinterlever apparatus comprising:
a first port for inputting or outputting a first polarized optical signal comprising a second signal with a first subset of channels, and a third signal with a second subset of channels;
a second port for outputting or inputting the second signal;
a third port for outputting or inputting the third signal;
a birefringent assembly optically coupled to the first, second and third ports;
a plurality of reflective elements positioned to reflect the first optical signal a plurality of times through the birefringent assembly along a first optical path or for reflecting the second and third signals a plurality of times through the birefringent assembly along second and third paths, respectively, thereby providing the first subset of channels with a different polarization than the second subset of channels;
a first beam splitter/combiner positioned to receive the optical signals from the birefringent assembly, for separating the first subset of channels from the second subset of channels or for combining the first subset of channels with the second subset of channels; and
a mirror positioned to reflect the first and second subsets of channels separately back to the birefringent assembly and the plurality of reflective elements for a second pass through the birefringent assembly along the second and third optical paths, respectively, that are parallel to the first optical path or to reflect the first and second subsets of channels together back to the birefringent assembly and the first reflecting means for another pass through the birefringent assembly along the first optical path;
wherein the first optical signal received via the first port is separated into the first subset and the second subset and directed to the second port and the third port, respectively, or wherein optical signals received via the second port and the third port are combined and directed to the first port.
Another aspect of the present invention relates to an apparatus comprising:
a birefringent assembly;
first reflecting means for reflecting an optical signal such that the optical signal makes multiple passes through the birefringent assembly following a predetermined path a first time;
first polarization rotator for reorienting the polarization of the optical signal after at least one of the passes through the birefringent assembly, whereby after making the multiple passes through the birefringent assembly for the first time only a first subset of optical channels in the optical signal have a first polarization; and
second reflecting means for reflecting the optical signal such that the optical signal traverses the predetermined path or a path parallel thereto for a second time through the birefringent assembly, in an opposite direction to the first time.